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Slowness over Ipsec vpn tunnel

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  • 1.  Slowness over Ipsec vpn tunnel

    Posted 09-02-2019 23:15


    We are facing an issue with with the tunnels one our Juniper SRX 240. We have a tunnel between Gibraltar and Israel and between London and Israel and whenever we try to copy a file from/to Israel to Gib/London, the file transfer is extremely slow. The speed of the transfer seems to be maxing out at around 355KB/s. The issues started just recently and since only a handful of people have access to the devices we are certain there have been no changes to the configuration on either side. We have checked the error counters on the FW but there aren't any building up and the cpu is in normal values. We bounced the tunnel but that had no positive effect. We also performed a manual failover to the standby peer but nothing changed in regards to the speed of file transfers.


    Any assistance would be greatly appreciated.


  • 2.  RE: Slowness over Ipsec vpn tunnel

    Posted 09-03-2019 02:19


    I would start tracing the exact trajectories of Your tunnels, to make sure it does not go via unexpected places, like Israel-Capetown-Brazil-Gibraltar.



  • 3.  RE: Slowness over Ipsec vpn tunnel
    Best Answer

    Posted 09-03-2019 08:40

    Hi Trasgu,


     In order to determine the cause of the slowness, please provide us with the following information.


    > Did you made any changes in the peer prior to this issue or any additional traffic introduced into the tunnel?

    > What is the Encryption method used for VPN? Advanced encryption can introduce latency is a network due to heavy processing.

    >  One of the major reason for latency can be fragmentation, so, please alter the MSS accordingly -


    Let me know if you face any difficulty.

  • 4.  RE: Slowness over Ipsec vpn tunnel

    Posted 09-05-2019 06:38

    Thank you guys, MSS is properly configured already. 

    We have seen abnormal slow upload speed on the internet line, and this is most likely causing this issue. 

    Hopefully everything will be back to normal once the ISP fixes the issue. 



  • 5.  RE: Slowness over Ipsec vpn tunnel

    Posted 09-05-2019 07:20

    Hi Trasgu,


    You're welcome. Let us know if you still face slowness once the issue is fixed on the ISP side.